This invention relates to a unit which effects optical recording and playback into or from a disc-shaped medium having a series of tracks or spaced tracks, in particular, to an optical recording and playback unit which performs both focus control to maintain a beam of light in focus on a pitted surface where vertical oscillation of a disk may occur during rotation of a disc-shaped medium, and a tracking control which causes the beam to follow the radial displacement of a track which may occur as a result of eccentricity in the rotation of the disc shaped medium, thus allowing the beam to be maintained in tracking relationship with a single track, and more particularly, to an optical recording and playback unit which achieves time axis control to maintain the tracking speed of the beam constant in addition to both of the abovementioned controls.
Known recording and playback apparatus perform both focus control and tracking control by utilizing a lens barrel including a light source and a lens system and which is supported by a resilient support. With this known apparatus, drive along the direction of the optical axis and in a direction transverse thereto has been achieved using separate, namely, two or three linear motors of the moving coil type. The provision of two or three motors, accompanied by an increased length in the optical path of the optical system which results from the individual location of the two or three motors in the direction of the optical axis, also tends to result in an increased size and a complex arrangement of the apparatus.